The invention relates to a method of producing an igniter for a gas generator and also relates to a charge sleeve for such igniter.
In igniters hitherto, a sleeve is inserted into the body of the igniter, which sleeve is sufficiently long to be able to receive a pyrotechnic ignition charge in the non-compressed state or as a suspension in fluid. By compressing the ignition charge or after evaporation of the solvent, the volume of the ignition charge is reduced, so that the edge of the sleeve projects axially with respect to the ignition charge. In further production, the sleeve is covered by a cap in order to close the sleeve. Hence, a cavity remains in the igniter, which is not filled by the ignition charge. This cavity increases the overall length of the igniter, which is a disadvantage especially with regard to the constant requirement for a reduction on the overall size of gas generators.
It is an object of the invention to provide an igniter with a small overall size.
This is achieved by a method of producing an igniter for a gas generator, which comprises the following steps: A pyrotechnic ignition charge is introduced via the open end into the charge sleeve such that an edge of the charge sleeve projects axially at the open end with respect to the ignition charge. The projecting part of the edge is shortened axially, and the open end is closed. The ignition charge can therefore be introduced, as usual, in loose form or as a suspension, the large axial length of the charge sleeve being necessary in order to firstly receive the overall quantity of the ignition charge, which is required for the igniter. After the reduction of the volume of the ignition charge, the edge of the charge sleeve projects axially with respect to the ignition charge. As the projecting part of the edge is now no longer required, this edge is shortened axially, in order to eliminate the cavity which is not filled by the ignition charge. Then the open end of the charge sleeve is closed by conventional methods. The overall length of the igniter can be distinctly shortened by this method, a reduction in length of approximately 2 mm being able to be achieved.
In a preferred method according to the invention, the charge sleeve consists of two parts, one of the two parts being a removable ring which comprises the edge and is removed after the ignition charge has been introduced. The ring is preferably placed onto the second part of the charge sleeve. The advantage of such a removable ring lies in that the axial shortening of the charge sleeve takes place without vibrations and shocks, which could impair the consistency of the ignition charge or even lead to ignition.
In another preferred method according to the invention, the charge sleeve can have a weakened zone running along its periphery, and the axial shortening of the projecting part of the edge of the charge sleeve takes place in that the projecting edge is separated, broken off or torn off. Also in this process, no violent shocks and vibrations take place, which could alter the consistency of the ignition charge. Also, other methods for shortening the edge are, of course, conceivable.
Preferably, the ignition charge is compressed before the axial shortening of the charge sleeve, in order to keep the volume of the ignition charge as small as possible and to obtain a density capable of ignition. Thus, through an axial shortening of the charge sleeve, a maximum reduction to the overall size of the igniter can be achieved.